Nowadays, there are several devices for taking samples of soft tissue, these devices being generally used to extract, in a minimally invasive way, a sample of an organ from a human or an animal for analysis purpose. This extraction operation is generally known as biopsy and the used device is known as a biopsy gun.
Such a sampling device comprises in particular a sampling needle formed by a cannula and a stylet, an arming mechanism placed on a body and a trigger also placed on the body of the device.
The arming mechanism is used to partially retract the needle towards the inside of the body of the device, the device is placed near the organ from which one wishes to take a sample, then the trigger is pressed so that the needle can penetrate into the organ. The needle being formed by a stylet and by a cannula, the stylet penetrates into the organ, the cannula then covers the stylet. This stylet comprises at least one notch receiving the tissue to be taken. When the cannula covers the stylet, the tissue sample is trapped in the notch and is cut. The unit is withdrawn so that the sample(s) arranged between the stylet and the cannula can be taken. An example of application of such a device is taking tissues of the prostate.
The arming of the needle is generally achieved in two phases, namely the arming of the cannula in a first phase and the arming of the stylet in a second phase.
During sampling of tissues, it is frequent that the person who carries out the sampling has only one free hand, the other hand being used to hold other medical devices such as for instance an echographic probe. In this case, it is important to be able to manipulate the sampling device with one single hand. The manipulation implies here the arming of the cannula, the arming of the stylet and the release of the shot allowing for the sample to be taken.
Among the existing devices, which enable manipulation with one single hand, one of them is described in the U.S. Pat. No. 7,153,275. This device is perfectly functional in most cases. However, problems may occur in certain circumstances. These problems can come from the fact that the stylet and the cannula are not perfectly aligned and that the stylet does not slide in a totally optimal way in the cannula. Indeed, an optimal sliding motion involves particularly tight manufacturing tolerances for the realisation of the parts of the biopsy gun. These tolerances can sometimes be difficult to maintain on parts made from plastic. This can lead to jamming of the needle, sometimes even to deformation of the latter. This has also as a consequence that the number of shots that it is possible to carry out with a device is reduced.
In order to minimise the problems linked to the jamming of the stylet in the cannula, a relatively powerful spring is foreseen for the cannula in order to propel the latter in an effective way. This has the drawback that a greater force is necessary to arm the device, which is unpleasant for the user. Despite such a spring, the needle may jam and bend so that the device becomes unusable.
This invention proposes to realize a tissue sampling device which has the advantages of the devices of the prior art i.e. it is possible to use this device with one hand. However, this device does not have the drawbacks of the systems of the prior art. Thus, the risk of jamming of the needle, as well as the risk of breakage or deformation, is strongly reduced or even eliminated.
Furthermore, and especially in implementations of the invention wherein the sampling device may be a single-use sampling device, particularly the risk of jamming of the needle and/or the cannula individually or in relation to each other is reduced or eliminated. This is at least partly because the sampling device, and particularly the movable parts thereof e.g. the needle and the cannula, is then assembled correctly during manufacture leaving no risks of a user putting the parts together in the wrong manner as could very well be the case with re-useable sampling devices. In addition, a single-use device is also significantly less prone to risks of contamination, e.g. by bacteria on a user's hands.
Moreover, as a single-use sampling device may enable production tolerances different from those of a re-useable sampling device, it is in most cases less costly to manufacture than such re-useable sampling devices. Thereby, the improved security mechanisms against unintentional firing of the sampling device according to the different implementations of the invention may be particularly, but not exclusively, suitable for single-use sampling devices in order to meet any potential risks due to such different production tolerances as mentioned above.